1. Field of the Invention
The present invention relates to a process for producing styrene-based polymers. More particularly, it relates to a process for an efficient, stable and continuous production of styrene-based polymers having a high degree of syndiotactic configuration.
2. Description of the Related Arts
Conventionally, styrene-based polymers having a stereostructure of atactic or isotactic configuration have been well known, but recently styrene-based polymers having a stereostructure of syndiotactic configuration have been developed, one of which, for example, is disclosed in Japanese Patent Application Laid-Open No. 187708/1987.
The styrene-based polymers having syndiotactic configuration solidify when a conversion reaches approximately 20% in the polymerization reaction, while the reaction continues until a conversion of approximately 70% is accomplished. Accordingly, if the polymerization reaction is effected in a reactor provided with agitating blades having conventional paddle blades, macro-particles with diameters of approximately 5 mm or more are formed when styrene-based polymers having a syndiotactic configuration are precipitated from the liquid-phase, and such particles lower the drying efficiency. Moreover, in the part of the reactor where the shearing force by the agitation cannot reach, these particles solidify into cakes, so that at the completion of polymerization reaction, polymer pieces remain adhered to the inner wall of the reactor, agitating blades, and objects such as thermocouples which project into the reactor.
Accordingly, almost all the processes for producing styrene-based polymers having syndiotactic configuration have heretofore been carried out by a batch system in which a tank type reactor provided with agitating blades, etc. has been used and no sufficient investigation has been done with respect to continuous polymerization techniques.